The present invention relates to a liquid crystal display device and an electronic apparatus.
Conventionally, as a mode most widely used in liquid crystal display devices, there is known a twisted nematic (TN) mode which is a normally-white mode. Recently, the TN-mode liquid crystal display devices have been advanced remarkably and image quality thereof has been improved up to the same level as CRT. However, the TN-mode liquid crystal display devices have a serious disadvantage that the viewing angle is narrow. A vertical alignment (VA) mode in which liquid crystal having a negative dielectric anisotropy is vertically aligned between a pair of substrates opposite to each other solved the disadvantage. The vertical alignment mode is currently applied to liquid crystal televisions, etc. to come in the market. The VA-mode liquid crystal display devices have characteristics of a wide viewing angle and a high contrast.
In the VA-mode liquid crystal display devices, there has been known that the wide viewing angle can be realized by employing a structure for dividing an alignment direction of liquid crystal molecules into a plurality of different directions in pixels. Here, examples of a specific structure for performing the alignment division include a structure where slits are formed in a transparent electrode such as ITO, etc. and a structure where protrusion portions are formed on the transparent electrode. There is disclosed a technique of controlling a direction in which the vertically-aligned liquid crystal falls down at the time of application of voltage, by providing the slits or protrusion portions (for example, see Patent Document 1).
Furthermore, in a conventional transflective liquid crystal display device, there was a problem that the viewing angle is narrow in transmissive display. This is because there is a restriction that reflective display should be performed only with one sheet of polarizing plate provided at an observer side since a transflective plate is provided on the inner surface of liquid crystal cells so as not to generate parallax, thereby reducing a degree of freedom in optical design. Therefore, in order to solve this problem, Jisaki et al suggested a new liquid crystal display device employing vertically-aligned liquid crystal in Non-Patent Document 1 described below. Features thereof are as follows:
(1) A “Vertical Alignment (VA) mode” is employed in which liquid crystal having a negative dielectric anisotropy is aligned vertically to a substrate and the vertically-aligned liquid crystal falls down due to application of voltage.
(2) A “multi gap structure” is employed in which the thickness (cell gap) of the liquid crystal layer is different in the transmissive display area and the reflective display area.
(3) The transmissive display area is formed in a regular octagon and a center of the transmissive display area on a counter substrate is provided with a protrusion so that the liquid crystal falls down in all directions. That is, an “alignment division (multi domain) structure” is employed.
Although in the above document, the protrusion is used as alignment control means for controlling the direction in which the liquid crystal falls down, there has also been a technique that an electric field is deformed by providing a slit in an electrode and the direction in which the liquid crystal falls down is controlled due to the deformation of the electric field.
There is also a transmissive liquid crystal display device employing the vertical alignment mode. Specifically, for example, a wide viewing angle is realized by dividing one pixel into a plurality of sub-pixels and forming convex portions at centers of respective sub-pixels on the counter substrate to make one pixel to multi domains (for example, see Patent Document 2). Features thereof are as follows:
(1) One pixel is divided into a plurality of sub-pixels.
(2) The shapes of the sub-pixels have a rotational symmetry (for example, circular shape, square shape, pentagonal shape, etc.).
In addition to the shapes of (2), by providing a convex portion at the center of the opened portion or the sub-pixel, the liquid crystal molecules are aligned in a radial shape from the center, thereby enhancing the alignment control power.
By adding chiral agent, the direction in which the liquid crystal is twisted is controlled, thereby preventing spotty stains due to the alignment failure.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 11-242225
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 200-202511
[Non-Patent Document 1] “Development of transflective LCD for high contrast and wide viewing angle by using homeotropic alignment”, M. Jisaki et al., Asia Display/IDW'01, p. 133-136 (2001)